The present invention generally relates to engines and more particularly, to a cylinder block construction of an engine having a pair of balancer shafts provided at opposite sides thereof, in which mounting portions for securing engine mounts thereto are increased in rigidity.
Conventionally, for example, U.S. Pat. No. 4,000,666 has disclosed an engine in which a pair of balancer shafts each having an unbalanced portion are disposed at opposite sides of a cylinder block and are rotated synchronously with rotation of a crankshaft at the number of revolutions identical with the number of revolutions of the crankshaft multiplied by either 1 or an integer of 2 or more such that unbalance of primary or secondary or more couples of forces or inertia forces resulting from reciprocation of each piston is controlled by centrifugal forces applied to the unbalanced portions.
Meanwhile, in the case where such engine is mounted on a motor vehicle, it has been so arranged that a skirt portion of the cylinder block is coupled with the body of the motor vehicle through the engine mounts.
However, in the known engine, such a problem arises that since the skirt portions of the cylinder block have low rigidity structurally in the cylinder block, mounting portions of the skirt portions, which are provided for securing the engine mounts thereto, are required to be reinforced sufficiently in order to restrict vibrations of peripheral portions of the engine mounts, thereby resulting in increase of weight of the engine.